diff --git a/server/hooks.go b/server/hooks.go
index ebf78c5..da5cf54 100644
--- a/server/hooks.go
+++ b/server/hooks.go
@@ -219,7 +219,7 @@ func (p *Plugin) MessageHasBeenPosted(c *plugin.Context, post *model.Post) {
     if personaDesc != "" {
         systemPrompt = "You are " + personaDesc + ". Respond in character. Only respond to the latest message — do not re-address earlier messages. Vary your openings and phrasing each time."
         if cfg.Brevity != "" && cfg.Brevity != "0" {
-            systemPrompt = "Reply in " + cfg.Brevity + " sentences or fewer. " + systemPrompt
+            systemPrompt = "IMPORTANT: Reply in " + cfg.Brevity + " sentences or fewer — no exceptions. " + systemPrompt
         }
         messages = append([]ChatMessage{{
             Role:    "system",